Hydraulically operable percussion jar



`lune l2, 1962 R. WSBROWN 3,038,548

HYDRAULICALLY OPERABLE PERCUSSION JAR R. W. BROWN HYDRAULICALLY OPERABLEPERCUSSION JAR June 12, 1962 5 Sheets-Sheet 2 Filed Nov. 6, 1957ATTORNEY June l2, 1962 R. w. BROWN HYDRAULICALLY OPERABLE PERCUSSION JAR5 Sheets-Sheet 4 Filed Nov. 6, 1957 INVENTOR.

Hob/fawn W Brow/7 June 12, 1962 R. w. BROWN HYDRAULICALLY OPERABLEPERCUSSION JAR 5 Sheets-Sheet 5 Filed Nov. 6, 1957 Hob/fawn VV. grow/7.

ATTORNEY tatcs riexas Fiied Nov. 6, 1957, Ser. No. 694,856 2 Claims.(Cl. 175-296) This invention relates to well jars and more partcularlyto hydraulically operable percussion jar mechanism -for use in a stringof drill pipe, well tubing, drill collar string or the like.

In the drilling and production of wells, such as oil and gas wells, itis often desirable to provide jarring mechanism incorporated in thedrilling string or tubing string which may be operated when necessary todeliver anV impact on the string in the event that the same shouldbecome stuck in the well bore, or for other reasons. Heretofore, suchjarring mechanism, as usually constructed, has been made up oftelescopingly arranged parts connected into the string for rotationtherewith and which are movable longitudinally relative to each other todeliver an impact to the string.

Jarring mechanism of this type, as heretofore commonly employed,however, possesses the disadvantage that some means must *be providedfor holding the parts against relative longitudinal movement duringnormal operation of the string; and which may be released bymanipulation of the string to place the mechanism in condition for thecarrying out of the jarring operation. Packing means must also beprovided between the longitudinally movable parts to prevent theentrance of well lluid into' or escape of fluid from the string. Anotherdisadvantage of jarring mechanism of the type heretofore com-monlyemployed is that usually only a single impact can be delivered at oneoperation of the mechanism, after which the mechanism must be resetbefore the next impact can be delivered. Moreover, in the operation ofjarring mechanism of this type the interval ibetween impacts isrelatively great yand after the delivering of one impact the stuckportion of the string or iish may move longitudinally independently ofthe portion of the string above the same during the resetting of theparts, so that there is danger that the effectiveness of the impact willbe lost by downward movement of the stuck portion during such resetting.

The present invention has for an important object the overcoming of theabove mentioned disadvantages by the provision of jarring mechanism inwhich the impact delivering means is enclosed within the string andjarring is accomplished without longitudinal movement of any part of thestring relative to any other part thereof.

Another object of the invention is to provide jarring mechanism whichdoes not reduce the strength of the string, whereby such mechanism maybe safely employed in the string during normal drilling operations.

A further object of the invention is` the provision of jarring mechanismwhich does not interfere with the circulation of well Huid through thestring during the drilling operation.

Another object of the invention is to provide jarring mechanism which isoperated by the circulation of Huid under pressure through the stringand which may be operated continuously and automatically as long as suchcirculation is maintained.

Another object of the invention is to provide a jarring mechanismoperable by a unidirectional input of fluid at the surface and in whichthe magnitude, frequency of impacts, and power delivered to the stringcan be controlled by the openator by varying the volume of fluid pumpedthrough the mechanism.

3,038,548 Patented June l2, 1962 A further ohject of the invention isthe provision of jarring mechanism of the kind referred to which may beoperated while the string is under tension, compression or torque or acombination of such stresses.

A still further and important object is to provide a mechanism whichwill impart to the drill string a series of mechanical impulses in onedirection alternating with hydraulic impulses in the opposed directionto produce -a strong vibratory motion in the string which is veryetective in freeing the bit or any part of the string which may becomestuck.

The above and other important objects and advantages of the inventionmay best be understood from the following detailed description,constituting a specification of the same when considered in conjunctionwith the annexed drawings, wherein- FIGURES 1A and 1B are fragmentaryvertical, central, cross-sectional views of `a preferred embodiment ofthe invention showing the same as applied to -a drilling string and withthe parts of the mechanism in the relative positions which they occupyat one stage of the jarring operation, FIGURE 1B being a downwardcontinuation of FIGURE 1A;

FIGURES 2A and 2B are views similar to those of lA and 1B, respectively,showing the parts of the mechanism in the relative positions which theyoccupy at another stage of the jarring operation;

FIGURE 2C is a cross-sectional View, on a somewhat enlarged scale takenalong the line ZC-ZC of FIGURE 2B, looking in the direction indicated bythe arrows;

FIGURES 3A and 3B lare views similar to those of FIGURES 1A and 1B,respectively, showing the parts of the mechanism in the relativepositions ywhich they occupy at still another stage of the jarringoperation; and

FIGURES 4A and 4B are views similar to those of FIGURES 1A and 1B,respectively, illustrating a somewhat ditferent form of the jarringmechanism of the invention and showing the parts in the relativepositions which they occupy at a stage in the jarring operationcorresponding substantially to the stage of operation shown in FIGURESlA and 1B.

Referring now to the drawings in greater detail, the jarring mechanismof the invention is illustrated in FIG- URES 1A, 1B, 2A, 2B, 3A and 3Bin connection with its application to a drilling string of usualconstruction, the mechanism having an upper tubular section 10 providedwith an externally threaded pin portion 12 at its lower end and a lowertubular section 14 provided with an externally threaded pin portion 16at its upper end. The jarring mechanism of the invention comprises atubular barrel or housing 18 whose opposite end portions are internallythreaded as indicated at 20 and 22 for the connection thereto of anupper tubular connector element 24 and a lower sub 27.

The upper connector element 24 is provi-ded with an externally threadedpin portion at its lower end for connection to the internally threadedupper end of the barrel with its lower end surface positioned to form aninternal annular downwardly facing impact face 28 within the upper endportion of the barrel.

A lower connector element 26 is provided which has an internallythreaded pin portion at its upper end for connection to the lowerinternally threaded box portion 25 of the tubular sub 27 whose upperexternally threaded pin portion 29 is threadably connected to the lowerend of the barrel.

At its upper end the upper connector element 24 is provided with aninternally threaded =box portion 32 for the connection thereto of thelower externally threaded end of the upper section 10, and the lowerconnector element 26 is provided at its lower end with an internally 3threaded box portion 34 for the connection thereto of the externallythreaded upper end of the lower section 14.

The upper connector element 24 has an enlarged, internal, upwardlyopening counterbore 38 therein which is in communication near its lowerend with the exterior of the element through one or more openings 40.

The tubular impact element or hammer 41 is movably positioned in thebarrel for longitudinal movement therein, and has a tubular extension 42at its upper end of reduced external diameter to provide an upwardlyfacing, annular, impact `face 43 on the impact element positioned tomove into and out of contact with the face 38. The extension 42 extendsupwardly into the upper connector element and into the counterbore 38thereof, and is of smaller diameter than the internal diameter of theconnector element 24 below the counterbore 38, to provide clearancebetween the extension and the upper connector element to form apassageway 44 externally of the extension. The barrel 18 also has one ormore openings 46 in communication fwith the interior and exterior of thelbarrel near its upper end and through which iiuid may ow through thepassageway 44 and through opening 40. Within the barrel 18 the impactelement 41 has an external enlargement 45 which carries a seal formingelement 47 in an external groove provided for the same, to form a uidtight seal between the impact element and the barrel below the openings46.

Within the counterbore 38 the extension 42 carries a piston 48 forming apart of the impact element and means is provided thereon, such as theO-rings 50 and 52 for Iforming a fluid tight seal between the piston andthe internal wall of the counterbore and between the piston and theextension.

The impact element or hammer 41 has a reduced externally threaded lowerend portion 54 to which a tubular valve actuating element 56 isthreadably connected at its upper end. At its lower end the valveactuating element 56 has an internally thickened portion 58 forming anupwardly facing, internal, annular shoulder 60.

A tubular valve 62 is movably positioned in the actuator 56 forlongitudinal movement therein, and extends downwardly through theinternally thickened portion 58 land into the sub 27. The portion of thevalve which is movably extended through the portion S8 of the actuatorand into the sub 27 is of smaller external diameter than the internaldiameter of the portion 58 but fits closely within the reduced bore inthe upper part of the sub 27. The valve has an upper end portion 64which is externally thickened to form an annular, external, dov/nwardly`facing shoulder 66 positioned to be engaged by the shoulder 60 of thevalve actuator 56 to move the valve upwardly with the impact element 41when the impact element reaches a predetermined point in its upwardtravel, and at its upper end the valve is formed with an externalannular ange 68.

An annular spring seat member 70 is movably positioned in the actuator56 in position to bear against the -upper end of a coil spring 72surrounding the valve 62 and whose lower end rests upon the shoulder 60.The spring seat member 70 has an internal flange 74 thereon positionedfor engagement with the external flange 68 of the valve so that thespring will be compressed upon upward movement of the valve actuator 56relative to the valve until the shoulder 60 of the actuator engages theshoulder 66 of the valve.

The sub 27 is formed with upper and lower counterbores 76 and 78,respectively, the counterbore 76 opening at its lower end into thebottom of the counterbore 78, and a tubular valve seat forming member 80is positioned in the counterbore 78 and has an upper end extension 82extending upwardly in the counterbore 76 and whose upper end is formedwith a valve seat 84 positioned for engagement with the lower end of thevalve 62 when the valve is in closed position. The valve seat member 80is `formed with one or more passageways 86 in communication with theinterior of the counterbore 76 exteriorly of the seat member and withthe interior of the seat member. The valve seat member also has aninternal tapered valve seat 88 located above the passageways 86 for apurpose to be explained hereinafter. A resilient washer shaped element90, such as a rubber washer, or the like, is positioned in thecounterbore 78 in contact with the lower end of the seat forming member80, and is held therein by contact with the upper end of the connectorelement 26 to retain the resilient member 90 in position.

The clearance between the exterior of the valve 62 and the internal wallof the sub 27 above the counterbore 76 is very small to form a fluidseal between the space 63 above the sub and the space within thecounterbore 76.

A go-devil 92 is provided for insertion into the drilling string formovement downwardly therein to a position extending through the valve62. The go-devil has an external enlargement 94 near its lolwer endwhich is provided with a tapered lower end face 96 positioned forengagement with the internal seat `88 of the valve seat men"- ber 80 toclose said member. At its upper end the godevil 92 has a fishing head 98by which the go-devil `may be retrieved from the spring by any suitablemeans, such as a wire line and grapple device. The go-devil may also beprovided with an externally enlarged portion 100, positioned to restrictthe downow of iluid through the impact element 41 in all positions ofthe impact element.

In making use of the invention constructed as described above, -the jarmechanism, without the go-devil 92, is incorporated in the drillingstring, or other string of pipe to be used in a well, and inserted withthe string into the well. With the jar mechanism so incorporated in thestring normal drilling or other operations may be conducted whilecirculating drilling fluid through the string and mechanism in thenormal manner. During such normal drilling operations the impact element41 will be in its uppermost position in the barrel 18, as shown inFIGURES 2A and 2B, and the valve 62 will be fully open and out ofcontact with the valve seat 84, as shown in FIGURES 3A and 3B.

When it is desired to carry out a jarring action with the mechanism, thego-devil 92 is inserted into the string at the surface and pumpeddownwardly under the inuence of the downwardly circulating drilling uidinto contact with the seat 88 to close the central opening through theseat.

Before the go-devil 92 has reached its seated position on the sea-t 88,the hammer element 41 could have been in either its lower position,shown in FIGURES 1A and 1B, or in an uppermost position yas shown inFIGURES 2A and 2B. The position of the hammer element belfore thego-devil seats is dependent upon the difference in pressure existingWithin the barrel 18 and that existing in the annular space between theoutside of the barrel and bore of the drilled hole. This difference inpressure will vary with the volume of fluid Ibeing pumped, the lengthand size -of opening from the valve seat member 80 to the bit, and thesize of the openings through the bit.

In most cases, the hammer element 41 will be in its uppermost position,FIGURES 2A and 2B, just prior to the go-devil landing on its seat 88.

Regardless of the position of hammer element just prior `to the landingof the go-devil on its seat, the jar will start to operate when thego-devil reaches its seat.

If the hammer element 41 is in its uppermost position, the beginning ofthe jarring cycle will be as follows:

The go-devil 92 lands on its seat 88 land plugs the central openingthrough the valve seat element 80. The externally enlarged portion 100of the go-devil is now positioned within the central bore of the hammerelement 41. The valve 62 is olf of its seat 84, and therefore fluid isfree to flow through the central bore of the hammer element, past therestriction created by the enlarged section 100 of the go-devil 92,through the valve 62, counterbore 76, ports 86, the bore of the sub 27and through the openings in the bit, not shown. The restriction in thebore of the hammer element caused by the enlarged section 100 of thego-devil 92 serves the specific purpose of creating a pressure drop pastit under iiowing conditions. This pressure drop causes a -higherpressure to exist above the top piston 48 than that existing below thehammer element, in the space 63. The higher pressure above the toppiston 48 acts on the area of this piston to create a force downward; atthe same time the iower pressure in the space l63 below .the hammerelement acts on an area dened by the outside diameter of the hammerelement 41 at the seal 47. A1- though the effective area of the toppiston 48 is less `than that defined by the seal 47, when the fluidvelocity has reached a given value the pressure difference between thespace above the top piston and the space 63 below the hammer element 41will be suiiicient to cause the hammer element to move down.

If the hammer element is in the lower position as shown in FIGURES lAand 1B just prior to the godevil 92 landing on its seat 88, then thestarting of the jarring cycle will be as follows:

As soon as the go-devil 92 reaches its seated position on the seat 88,downward flow of iluid through the mechanism will be suddenly checkedcausing a rapid increase in pressure above the seat 88. Since there isno iow of liuid at this time, there will be no pressure differentialexisting between the space above the topV piston 48 and the space 63`below the hammer element. rIlherefore the static pressure existinginside of the jar mechanism will be constant throughout the length ofthe mechanism. This high static pressure will act on the cross sectionalarea of the ham-mer element 41 at the seal point 47 to create an upwardforce on the hammer element. At the same time, a downward -force will becreated on the top pis-ton 48 and will have a value equal to the crosssectional area of the top piston multiplied by the static pressure.However, since this latter area is less than the cross sec- -tional areaof the hammer at Ithe seal point 47, the resulting force on the hammerelement 41 will be upward.

Regardless of `the position of the hammer 41 when the go-devil 92 rstseats, the jarring mechanism will start to operate. The first few cycleswill be relatively slow with intermittent hesitatons or a stutteringaction. These rst few stuttering cycles represent the transition from asteady ow condition before the go-devil 92 became seated to a steadydynamic state of intermittent flow. The starting operation under the twopossible conditions which could exist having -been explained, theoperation of the mechanism after a steady dynamic state has been reachedwill now be explained in more detail.

Let it be considered that each cycle starts with thev parts of themechanism in the position as shown in FIG- URES lA and 1B. At this pointof the cycle, the valve 62 is on its seat 84 and the hammer element 41is in one of its lower positions so that the impact face 43 ispositioned away from the impact face 28. With the parts in thisposition, no flow can exist through the mechanism, and therefore, a highwater hammer pressure exists within the interior of the jarringmechanism. This pressure will act on the cross sectional area of thehammer element 41 at the seal point 47 to force the hammer upward. Asthe hammer moves upward under very rapid acceleration, the valve :62remains stationary on its seat 84 because the static pressure above thevalve is much higher than that existing below the valve seat element 82.During the upward travel of the hammer, the upper end of the valvespring 72 is being held stationary by the shoulder 68 on the valve 62and the spring seat 70, while the lower end of the valve spring is beingforced upward by the enlarged section 5S at the lower end of theactuator 56. Therefore, it may be seen that the valve spring 72 is beingcompressed as the hammer element 41 moves upward. A short distancebefore the hammer impact face 43 strikes the anvil impact face 28, theupward facing shoulder 69 formed by the thickened section 58 at thelower end of the actuator 56 strikes the shoulder 66 formed on the valve62. When these .two latter faces make contact, the valve is jerked offof its seat 84, thus establishing a passage for uid to flow between thelower end of the valve 62 and its seat 84. Immediately thereafter, theimpact face ofthe hammer element 43 strikes the impact face 28 of theanvil. The position of the parts is now as shown in FIGURES 2A and 2B.Circulation through the impact 4mechanism has no-w been established sothat the pressures existing above the valve seat 84 and those existingoutside and below the valve seat will now become balanced. As thesepressures balance, there no longer exists the force tending to hold thevalve 62 on its seat. Therefore, the spring 712 which had formerly beencompressed will lift the valve 62 upward with respect both to the hammer41 and the valve seat 84, thus fully opening the space within thecounterbore76 to carry fluid therethrough, through the ports 86, thebore of the sub 27, and hence on through the openings in the bit. Theupward stroke of the hammer has now been completed and has resulted intransferring the kinetic energy existing in the hammer to the drillstring. After the hammer strikes the anvil and the valve 62 is aconsiderable distance off of its seat 84, the fluid velocity through4the impact mechanism will increase, and in so doing will cause apressure differential lto exist between the area above the top piston 48and the space 63 below the hammer eley ment 41. This pressuredifferential is caused principally by the enlarged section 10ft` nearthe upper end of the go-devil which enlarged section remains within thecentral bore of the hammer 41. As the iluid velocity through the bore ofthe hammer increases the pressure loss past this restriction increasesapproximately to the second power of the fluid velocity. Thus, when thepressure differential existing between the area above the top piston 48and the area below the hammer element, for example in the space 63,reaches a given value, the forces acting on the hammer element 41 willserve to force it downward. This -may be understood by considering thebalance of forces acting on the hammer element 4l. Since the`hydrostatic head existing within the impact mechanism is equal to thatexisting outside of it and within the bore of the drilled hole, thesehydrostatic pressures will cancel out and need not be considered indetermining the net forces acting on the hammer. Since the hydrostaticpressures will cancel and therefore any value may be as-v signed to themwithout affecting the results in calculating the direction of netforces, a value of zero will be assigned to the hydrostatic head inorder to simplify the problem. A-t any instant during the cycle, theforces acting upwardly on the hammer element will be the product of thecross sectional area of the hammer at the seat point 47, multiplied bythe pressure exis-ting below the hammer element which will be equal tothat existing at any point below the seal 47 and above the valve seat84. The force acting downward on the hammer will be equal to the productof the cross sectional area of the top piston 48, multiplied by thepressure existing just above this top piston. Since the cross sectionalarea of the top piston is` always less than that of the hammer, it isobvious that the pressure above the top piston rnust be considerablyhigher than that below 4the seal point 47 on the hammer for theresulting net force to be downward. As explained above, when the fluidvelocity reaches a predetermined value,

the pressure above the top piston will be sufficiently greater than thatbelow the hammer seal 47 so that the product of this higher pressure andthe cross sectional area of 'the top piston will be greater than theproduct of the cross sectional area of the hammer and the pressureexisting below the hammer. At this time, the hammer will start to movedownward. l ust after the hammer starts on its downward return stroke,the parts will assume the positions shown in `FIGURES 3A and 3B. Thespring 72 has now extended to it-s full length as limited by thedistance between the upward facing shoulder 60 of the actuator 56 andthe lower face of the spring seat 74 so that the valve 6.2 and thehammer element 41 are moving at the same velocity. The valve 62approaches its seat 84, `and at a given distance from the seat, it willsuddenly jump 4to closure, thus blocking circulation through the impactmechanism. This sudden checking of fluid ow will cause a pressureincrease, or water hammer pressure, to exist throughout the inside ofthe impact mechanism. The high static pressure, now reformed, will beequal throughout the length of the mechanism and therefore equal at apoint above the 'top piston 48 and below the seal 47 on the hammer sothat the net forces acting on the hammer are again upward. This may beeasily understood by considering that the pressures acting on the crosssectional area of the hammer and the cross sectional area of the toppiston are identical, but the cross sectional area of the hammer 41 islarger than that of the top piston 4S, therefore, the net result is anupward force. After the valve 62 seats, the hammer will first bedecelerated and come to a stop. `its direction will then be reversed asit is again accelerated upward to start a new cycle.

Throughout the operating cycle, the holes 40 in the connector 24, andthe holes 46 in the barrel 18 serve to allow iluid to be freelydisplaced as the hammer 41 moves up and down. They also serve thepurpose of allowing the difference of pressure between that existingwithin the mechanism and that existing outside of the mechanism to acton the top piston and the cross sectional area of the hammer to createthe net unbalance of forces as discussed above.

Each time the valve 62 closes, the rapidly moving column of iluid withinthe drill string is suddenly stopped. This results in a strong reactiondownward so that the net result of the mechanism is to createalternately a mechanical impulse upwardly and then a hydraulic reactiondownwardly. This transmits to the drill string an intense and highfrequency vibration which is very effective in freeing the bit or anyother components of the drilling assembly which may become stuck in thedrilled hole.

It may be seen in the illustrations that, by the proper spacing of thevalve 62 with respect to the actuator 56 and the valve seat 88, thehammer element may be made to alternately strike the anvil face 28 andthe upper face 30 of the connector 27. This would result in both upwardand downward mechanical impulses being transmitted to the drill string.Also, by a slightly different spacing of the above elements, themechanism can be adjusted to strike only the upper face 30 of theconnector 27 at each cycle resulting in transmitting to the drill stringalternate mechanical and hydraulic impulses each of which is directeddownward.

A somewhat diierent -form of the invention is illustrated in FIGURES 4Aand 4B, wherein the barrel 18' is connected at its upper end in the samemanner as previously described to the upper tubular section of thedrilling string by means of an upper connector element 24' similar tothe connector element 24, and the lower end of the barrel is providedwith an externally threaded pin portion 102 for the connection theretoof an upper end box portion 104 of a lower connector element or sectionof the string.

Near its lower end the barrel is formed with an internal counterbore 106of reduced diameter within which a seat forming element 108 is located,which may be provided with an annular insert 110, forming a valve seat.

The connector element 24 has an internally enlarged counterbore 112,which opens upwardly at the upper end of the element.

A longitudinally movable, tubular impact or hammer element 41 ispositioned in the barrel 18', and has an externally reduced upper endextension 42' to provide an external, annular, upwardly facing impactshoulder 111 positioned to engage the lower end face of the connectorelement 24' and which extends upwardly into the counterbore 112 andcarries at its upper end a piston 48'. Suitable seal kforming means,such as the O-rings 54) and 52 are provided on the piston 48 in annulargrooves provided for the same, in position to form fluid tight sealsbetween the extension 42 and the piston and between the piston and theinterior wall of the counterbore 112. Suitable seal forming means, suchas that shown at 47 is also provided positioned in an external groove inthe impact element 41 to form a fluid tight seal between the element andthe interior wall of the barrel 18'. The impact element 41' also has anexternally reduced downward extension 114 which is provided with one ormore openings 116 therein in communication with the interior of theimpact element and leading to the exterior thereof. Below the openings116 the impact element has an internal, annular, upwardly facingshoulder 11S.

A tubular bushing 120 is positioned in the lower end of the impactelement, which bushing has an external enlargement in its upper endforming an external, annular downwardly facing shoulder 122 positionedfor engagement with the shoulder 118.

A longitudinally movable, tubular valve 124 extends through the bushing12) and has at its upper end a tubular cap 126 forming a shing head, andat its lower end an external shoulder 130 upon which the lower end ofthe bushing 120 is seated. The valve 124 is closed at its upper end ybya tapered plug 132. The lower end of the valve has a bevelled end facewhich may be provided with an annular insert 134 positioned for contactwith the insert 110 of the seat forming element 108 when the valve is inits closed position.

A coil spring 136 surrounds the valve 124 which spring is seated at itslower end upon the upper end of the bushing 120 and bears at its upperend against the lower end of the cap 126.

The barrel 18 has an opening 138 in communication with the interior ofthe barrel just below the lower end of the connector element 24' andwith the exterior of the barrel, and the extension 42 is of somewhatsmaller external diameter than the internal diameter of the connectorelement to provide a passageway 140 through which fluid may tlow betweenthe interior of the counterbore 112 beneath the piston and the exteriorof the barrel 18' through the opening 138.

In the use of the form of the invention illustrated in FIGURES 4A and4B, the jarring mechanism, with the valve 124 and its bushing 120 andspring 136 removed, is connected into the drilling string in a mannersimilar to that explained in connection with the form of the inventionpreviously described, and lowered into the well bore with the string.The drilling operation may then lbe conducted in the usual manner byrotating the string while circulating drilling luid therethrough.

In the event that it is desired to carry out a jarring operation withthe mechanism, the valve mechanism may be inserted into the string andpumped downwardly therein with the drilling fluid until the valve isseated on the seat forming element 108.

As soon as the valve reaches closed position the downward ow of fluid inthe string `will be suddenly cheeked, whereupon the pressure of thedrilling iluid causes an upward movement of the impact element 41' tomove the impact shoulder 111 into contact with the lower end face 113 ofthe connector element 24' to deliver an upward jar on the string. Duringthe upward movement of the impact element the internal shoulder 122thereof engages the external shoulder 118 of the bushing 120 to move thebushing upwardly to compress the spring 136, whereupon the valve 124will be lifted to open position.

Upon opening of the valve the downward flow of Huid through the `stringwill be resumed to permit the impact element to return to its downposition under the influence of gravity and the downward pressure offluid on the piston 4S. During such downward movement of the impactelement the bushing 120 moves downwardly under the inlluence of thespring 136 and the valve 124 is held open until the impact elementreaches a lowered position. As soon as the valve again reaches closedposition the downward ow of fluid is again suddenly checked to produce awater hammer pressure build up to move the impact element upwardly tostrike the lower end face 113 to deliver another impact on the string.

By selecting the proper dimensions of the working parts of the mechanismit may be adapted to operate over a wide range of fluid volumes andpressures, thus enabling both the magnitude and the frequency of impactto be controlled by the operator by merely adjusting the speed of thepumps at the surface.

`It will -thus be seen that the invention provides jarring mechanismwhich is automatically operated by the pressure and rate of Iflow of thecirculating fluid in the string and which operates entirelyindependently of the rotary or longitudinal movement of the string.

While the invention is disclosed herein in connection with certainspecific embodiments of the same, these are intended by way ofillustration only, and various changes can be made in the constructionand arrangement of the parts within the spi-rit of the invention `andthe scope of the appended claims.

Having thus clearly shown and described the invention, what is claimedas new and desired to secure by Letters Patent is l. Jarring mechanismcomprising a tubular barrel adapted to be connected into a string ofpipe for insertion therewith into a well bore, la tubular impact elementmovably positioned in the barrel for longitudinal movement therein andhaving an upwardly facing surface and a downwardly facing surface whosearea exceeds that of the upwardly lfacing surface, means restricting the`flow of liuid downwardly .through the barrrel, means subjecting saidupwardly and downwardly facing surfaces, respectively, to the iluidpressure in the barrel upstream and downstream, respectively, of saidrestricting means, means forming an impact face in the barrel positionedto be engaged by the element upon upward movement of the element, meansforming a valve seat in the barrel below said restricting means and theelement and through which Huid may flow downwardly through the barrel, atubular valve movably positioned in the barrel for movement to oneposition to close the seat against downward flow of iluid therethroughto cause the fluid to exert an upward force on said element to move theelement upwardly, and to another position to open the seat, means on thevalve and element positioned for coaction upon upward movement of thee-lement to move the valve to open position, whereby the pressure actingon the downwardly facing surface is reduced and the element is loweredby the pressure acting on its upwardly facing surface, the valve movingto close the seat as the element is lowered.

2. larn'ng mechanism comprising a tubular barrel adapted to be connectedinto a string of pipe for insertion therewith into a well bore, atubular impact element positioned in the barrel for longitudinalmovement therein and having upwardy facing surface exposed to thepressure of fluid in the barrel and a downwardly facing surface oflarger area than said upwardly facing surface exposed to such pressure,means for restrict-ing the flow of iluid through the barrel at alocation to cause a difference in the pressure exerted by the fluid onsaid surfaces to cause the element to move downwardly, means forming animpact face in the barrel positioned to be engaged by the element uponupward movement of the element, and means for closing the barrel againstthe downward flow `of fluid therethrough upon downward movement of theelement, at a location to cause equalization of the pressure exerted bythe fluid on said surfaces to cause the element to move upwardly and for`opening the barrel to `such ow upon such upward movement of theelement.

References Cited in the file of this patent UNITED STATES PATENTS1,892,517 Pennington Dec. 27, 1932 2,756,723 Bassinger July 3l, 19562,786,451 Dulaney Mar. 26, 1957 2,813,516 Dulaney Nov. 19, 1957

